Laser ablation is a method to clean or refresh surfaces by applying laser energy to the surface to remove surface contaminants or layers. The laser is tuned to selectively ablate or remove surface contaminants or layers while leaving the underlying surface material intact. The effectiveness of laser ablation is substantially due to the laser energy absorbed at the surface. The proper amount of energy should be applied to ensure that the underlying surface remains intact while a sufficient amount of contaminants are removed.
The effectiveness of laser ablation is determined by factors such as the laser irradiance (surface density of laser power), the laser fluence (surface density of accumulated laser energy), the laser wavelength, material to be ablated (surface contaminants or layers), surface material, and surface shape. In particular for large surfaces and surfaces with significant 3D (three dimensional) shapes, a basic raster scan of the surface may produce areas that could potentially be over ablated or under ablated, for example due to a mismatch between the surface outline and the rectangular raster shape (e.g., not ablating edges of the surface or ablating support structure beyond the edges of the surface), shadowing by surface features (e.g., under ablating surface areas obscured by nearby protrusions, and/or non-uniform application of laser energy (e.g., over or under ablating a curved surface based on non-linear traversal time of the laser beam across the curved surface).
Hence, conventional laser ablation suffers from over ablation and under ablation, especially when the surface to be ablated becomes large relative to the width of the laser sheet and when the surface includes significant 3D features.